Objective Diabetic cardiomyopathy is one of the most serious complication of diabetes mellitus. Cell injury and apoptosis of myocytes are involved in diabetic cardiomyopathy. As activation of toll- like receptor 4 (TLR-4)/myeloid differentiation factor 88 (Myd88) signalling pathway which triggers cell apoptosis is correlated with generation of reactive oxygen species (ROS), it is logical to speculate the activation of TLR-4/Myd88 signalling pathway in myocytes play a role in diabetic cardiomyopathy. It is mentioned production of ROS contributes in onset, development and progression of diabetic cardiomyopathy. Selenium (Se) is an important trace element which is known to protect against ROS related cell injury by its antioxidant property. In this study, we investigated protective and anti- apoptosis effects of selenium on cardiomyocytes via ROS and TLR-4/Myd88 signalling pathway.
Methods Myocytes isolated from neonate rats were cultured whether in standard medium or high glucose medium (concentration of glucose = 25.5mM) to mimic sustained hyperglycemia in diabetic cardiomyopathy. Sodium selenite solution was applied to myocytes after incubation of high glucose medium. ROS was monitored by cell fluorescent staining of 2.7- dichlorofluorescein (DCFH-DA); activity of cellular glutathione peroxidase (GPx) was measured spectrophotometrically; apoptosis of myocytes was examined by flow cytometry; expression of TLR-4, Myd88, apoptosis-inducing factor (AIF) and Caspase-3 were assessed by real- time PCR and western blotting.
Results We found increased high glucose- induced cell apoptosis and up-regulated molecular expression of TLR-4/Myd88/AIF/Caspase-3 cascade, accompanied by increase of ROS generation. We also showed that supplement of selenium attenuated cell apoptosis of high glucose incubated myocytes, and mechanically, the protective effect was found dependent on attenuating oxidative status by decreasing level ROS, increasing activity of GPx, as well as inhibition of molecular expression of TLR-4/Myd88/AIF/Caspase-3 cascade in myocytes.
Conclusions These results suggest activation of TLR-4/Myd88 signalling pathway plays an important role in high glucose-induced cardiomyocyte apoptosis. Additionally, by modulating TLR-4/Myd88 signalling pathway which is linked with ROS formation, selenium exerts its antioxidative and anti-apoptosis effects in high glucose incubated cardiomyocytes.